// ------------------------------------------------------------
// A small program demonstrating how to remove every Nth element
// from a List[T] using clear, expressive Scala patterns.
// ------------------------------------------------------------
object RemoveEveryNthApp {
/*
removeEveryNth returns a new List[T] with every Nth element removed.
Scala lists use zero‑based indexing, so we check (index + 1) % n != 0
to keep elements that are *not* in the Nth position.
The variable "size" captures the list length before the loop,
which avoids repeatedly calling items.size inside the loop.
A mutable ListBuffer is used internally for efficient building,
and then converted back to an immutable List at the end.
*/
def removeEveryNth[T](items: List[T], n: Int): List[T] = {
if (n <= 0)
throw new IllegalArgumentException("n must be a positive integer")
val size: Int = items.size // capture size once
val buffer = scala.collection.mutable.ListBuffer[T]()
var i: Int = 0
while (i < size) {
if ((i + 1) % n != 0) {
buffer += items(i)
}
i += 1
}
buffer.toList
}
/*
main demonstrates the function with a simple example.
Keeping main small and focused makes the program easy to extend.
*/
def main(args: Array[String]): Unit = {
val data: List[Int] = (1 to 20).toList // Example list: numbers 1–20
val n: Int = 3 // Remove every 3rd element
val cleaned: List[Int] = removeEveryNth(data, n)
println(s"Original: ${data.mkString(" ")}")
println(s"After removing every $n-th element: ${cleaned.mkString(" ")}")
}
}
/*
run:
Original: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
After removing every 3-th element: 1 2 4 5 7 8 10 11 13 14 16 17 19 20
*/
